Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 190113 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 913 PM EDT Tue Apr 18 2017 .SYNOPSIS... High pressure will build over the area through early Wednesday. The next cold front will cross the area Friday afternoon. High pressure builds over New England for the weekend while low pressure moving in from the west will impact the Mid Atlantic Sunday. && .NEAR TERM /THROUGH WEDNESDAY/...
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A pressure surge will continue across the Mid-Atlantic region this evening as high pressure over northern New England moves southwestward. SE winds have increased to 10-15 mph with gusts 20-25 mph this evening. Clouds will increase late tonight as warm air advection occurs aloft. Light rain is expected to develop across the mountains west of the Blue Ridge and progress eastward Wed morning. Coverage remains in question as most guidance keeps light rain west and south of Baltimore/Washington metros through Wed afternoon. Cant rule out a passing shower as high pressure moves eastward.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
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Some light rain is still possible in the evening with a lull/break in precip late Wed night. Low clouds and fog are likely to be the main issue late Wed night. Chances for showers and t-storms increase Thu as instability builds and a lee-side trof develops. Coverage is expected to remain scattered with low risk of severe wx due to weak shear.
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&& .LONG TERM /FRIDAY THROUGH TUESDAY/... Cold front pushes towards the Mid-Atlantic, bringing scattered showers on Friday. Conditions will be become drier behind the front. High temperatures will be in the 70s and 80s, and lows will reach the 40s and 50s. Dry conditions continue into Saturday, maybe some showers over higher elevations... and PoPs increase over our CWA Saturday night as a low pressure system approaches from the west. High temperatures will be in the 50s and 60s... low temperatures overnight in the 40s and 50s. Guidance is in disagreement with the track of this low pressure between Sunday and Monday. GFS brings it slower and moving across the Mid-Atlantic with PW over one inch, while the Euro moves it faster and PW below one inch. Expecting dry conditions behind this system. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
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SE winds expected this evening with gusts up to 20 kts through midnight. Winds will slowly decline into Wed morning. Clouds increase late tonight with bkn- ovc035 cigs at KCHO and then at all other terminals after 12Z Wed. Potential for MVFR/IFR cigs/vsbys late Wed night into Thu morning. Risk of t-storms Thu afternoo and early evening. Showers possible on Friday as front pushes through our area. Drier conditions expected on Saturday. Showers return Saturday night into Sunday. Sub-VFR conditions possible at times, mainly Friday and Sunday with wind gusts reaching up to 20 kt for parts of this period.
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&& .MARINE...
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A pressure surge across the region has led to an increase in SE winds on all the waters. A SCA is in effect through 2 AM. Winds are expected to diminish into Wed morning however will need to monitor closely as SCA may need to be extended into the early morning hours. Winds should remain below SCA through Thu. SCA then more likely Thu night and Fri. Showers possible on Friday as front pushes through our area. Drier conditions expected on Saturday. Showers return Saturday night into Sunday. Sub-VFR conditions possible at times, mainly Friday and Sunday with wind gusts reaching up to 20 kt for parts of this period.
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&& .TIDES/COASTAL FLOODING...
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An onshore flow will continue through Wednesday. A pressure surge has caused the onshore flow to strengthen this evening. This has caused tidal anomalies to jump to between one-half and one-foot above normal. These anomalies should remain in place through Wednesday...which will cause water levels to approach minor flooding thresholds near high tide. Did not go with an advisory at this time with the latest forecast keeping water levels just below these thresholds. This is because the onshore flow may weaken a bit overnight into Wednesday behind the pressure surge. However...confidence is low and the anomalies will have to be monitored overnight.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 2 AM EDT Wednesday for ANZ530>543.
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&& $$ SYNOPSIS...LFR NEAR TERM...HSK/LFR SHORT TERM...LFR LONG TERM...IMR AVIATION...HSK/IMR/LFR MARINE...HSK/IMR/LFR TIDES/COASTAL FLOODING...BJL

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